Advanced radio cells AR1255, Руководство по физическому планированию и установке, Страница: 20 / 48

March 1, 2002 Page D3
The frequencies displayed in Table D1 were chosen such that the resulting signal as received by
the modem corresponds to a standard EIA CATV channel. This is because the modem, when not
properly initialized or when it has lost track of the downstream signal, will “step” through the
standard EIA channel list looking for a downstream signal. Alternatively, the modem may be
optioned through its administrator interface to lock onto a specific downstream frequency,
removing this requirement.
When the ARCi hub antenna is utilized in an MMDS repeater application its frequency conversion
(from upconverter output to carrier output) can be factory modified
3
to meet the requirements of
the MMDS transverter frequency plan. Contact the ARCi factory for more information on
alternative frequency plans.
Table D1 – ARCi Standard Downstream Frequency Plan
Upconverter Carrier Modem Modem
center freq. (MHz) center freq. (MHz) center freq. (MHz) EIA Channel
481 5729 429 58
487 5735 435 59
493 5741 441 60
499 5747 447 61
505 5753 453 62
511 5759 459 63
517 5765 465 64
523 5771 471 65
529 5777 477 66
535 5783 483 67
541 5789 489 68
547 5795 495 69
553 5801 501 70
559 5807 507 71
565 5813 513 72
571 5819 519 73
Adjacent Sectors
The ARCi standard hub antenna has been described above as having a half power horizontal
beam width of 60 degrees. But, the energy of the antenna does not simply cut off at 30 degrees
in horizontal pattern from the centerline of the antenna. Rather, the energy falls off as the angle
from the centerline increases. This means that a subscriber in the vicinity of 30 degrees
clockwise from antenna A will also be in the vicinity of 30 degrees counterclockwise from adjacent
antenna B. Subscribers in the overlap zone – especially if they are relatively close to the hub –
will receive downstream signals from both adjacent hub antennas. This will cause unacceptable
3
The ARCi subscriber unit has a fixed conversion that cannot be modified.